You cannot delete a stage outright but you can overwrite it with an adjacent stage.
1. To delete stage, go to the Time screen.
2. On the timeline at the bottom of the screen, click one of stages adjacent to the stage you want to delete. This is to say, select the stage that you want to use to overwrite the stage you want removed.
The editable stage will display, hovering above the timeline.
The stage will have a green dot to the left and a red dot right. These will be used to select the start or end event of the stage, respectively, on the timeline below.
3. Drag and drop the stage's start marker (green dot) or end marker (red dot) over the event that starts or ends the adjacent stage (the stage you want to overwrite).
Left-click on the green or red dot and while continuing to press the left-click button, drag it directly over the icon of the adjacent stage’s start or end event, in the timeline below. Once positioned over the icon, release the left-click button.
4. Click OK to drop the edited, extended stage back into the timeline below.
5. When prompted, click Yes to confirm that the stage should be overwritten.
The timeline should reflect the extended stage, with the stage that was adjacent to it having been overwritten.